The use of cam or sprag clutches in indexing applications is well known. Every clutch has an upper limit to its indexing performance regulated by the speed at which the cam can respond to the input. If the cam cannot respond quickly enough the cam will slide on the race for some distance until it rocks and engages the races to transmit torque. The upper speed at which this sliding occurs is regulated by the energizing force on the cam, e.g. the spring force that pushes the cam against the inner and outer races, and the inertia of the cam and cage that must be moved to allow the cam to rock into engagement with the races. Highest indexing rates are achieved by increasing the energizing force and/or reducing the inertia of the parts that must be accelerated and decelerated.